Hazardous materials crews scrambled to locate the source of a chemical leak at a downtown Vancouver business complex for most of Monday, unable to pinpoint the exact source of the hydrogen fluoride gas that sent five people to hospital.

Lt. Carol Messenger of Vancouver Fire and Rescue Services said the fumes originated from and were most highly concentrated in a third-floor spa at a complex at 1008 Homer St.

No one at the spa could be reached for comment by press time.

Investigators believe the fumes could be a refrigeration product, possibly combined with rust in the piping causing the gas to leak.

“It will be in effect as long as the whole scene is closed down, which can be quite some time,” Messenger said.

A Shoppers Drug Mart outlet and other businesses at the complex were evacuated just before 10 a.m. Paramedics treated three people on scene and another five people were taken to the nearby St. Paul’s Hospital. An adjacent TD Bank was evacuated in the afternoon.

Many employees and customers in the complex left voluntarily, Messenger said. It’s unclear how many people were in the building when the gas was detected.

St. Paul’s spokesman Dave Lefebvre said staff treated and released four people “pretty quickly,” but he couldn’t comment on what symptoms they suffered.

“It can be a variety of things a person can experience, from dizziness, lightheadedness, nausea to more serious internal burning of the respiratory tract,” he said. “That’s not unlike smoke inhalation.”

According to Health Canada information, hydrogen fluoride is a “colourless, pungent, acrid liquid or gas” highly soluble in organic solvents and in water, where it forms hydrofluoric acid.

The B.C. Centre for Disease Control was notified of the incident, but it hadn’t confirmed for itself what the gas was by press time.

Messenger said crews continued to inspect the building’s piping and elevator shaft as of Monday evening. She added until the source is located, the building and nearby road space would remain closed to the public.